> We observed no evidence that obesity contributed to a decline in IQ, even among obese individuals who displayed evidence of the metabolic syndrome and/or elevated systemic inflammation.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3813310/
> Overall there was an inverse FIQ/obesity association, except in pre-school children. However, after adjusting for educational attainment, FIQ/obesity association was not significantly different. A lower FIQ in childhood was associated with obesity in later adulthood perhaps with educational level mediating the persistence of obesity in later life.
There's not an onus of proof on someone who says the sky is blue or water is wet. We need a certain foundation of understanding to have productive conversations.
And we all have stuff to do. Suffice it to say, there is plenty of supporting evidence for the claims.
> Please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize. Assume good faith.
Female obesity is known to lead to preganancy complications which cause cognitive deficits.
Obesity in general is known to cause systemic inflammation which affects cognition and speeds up dementia.
The opioid crisis and various other types of drug abuse lead to brain damage.
Various nutritional deficiencies could play a role. Historically, iodine deficiency caused the condition of cretinism, but sub-clinical deficiencies can lead to more subtle effects.
Sleep deprivation is known to cause cognitive deficits, and electronic lights and jobs with nocturnal schedules are more common now. Light pollution and spending too much time indoors during the day throws off our circadian rhythms.
We still have various types of neurotoxins plaguing our environments. More people are living in urban environments now, which causes greater exposure to automobile exhaust. Coal plants are still spewing neurotoxins. Lead pipes are still common in many cities.
High indoor CO2, from poor ventilation, is known to cause cognitive deficits.